U.S. Pat. No. 3,856,196 discloses a device for severing web-shaped material, in particular paper webs for producing cards. Prior to being fed to a cutting mechanism that cuts the web into individual sections, the web is passed between a brake roll and an angled plate or a trough in order to relieve the web of part of the tension produced by a feeding mechanism arranged in advance thereof, thus preventing the formation of burrs or other deformations on the web perforations that may interact with the feeding mechanism.
Another cutting device is known from U.S. Pat. No. 4,693,151. According to this patent a cutting mechanism serves to sever record members from a web for subsequent use as tags, for example. The cutting mechanism cuts the longitudinally traveling web transversely with coacting knives. The cutting mechanism is arranged in the interior of a housing having an entrance section in the form of an opening for introducing the web. The severed record members of the web are then fed to a stacker disposed in the housing interior.
Operating, for example, as label or tag cutters, cutting mechanisms of this type are arranged at the output end of a printer unit in which portions of the continuously fed web of flat material are printed upon. In the cutting mechanism, consecutive printed portions of the flat material web are severed essentially transversely to the direction in which the web travels.
The severing cut which extends transversely to the feeding direction is conventionally performed by a rotating cutter roll whose axis of rotation is normal to the feeding direction and parallel to the plane of the web. At least one blade member provided on the circumference of the cutter roll extends preferably in a slightly spiral fashion so that in operation of the cutting mechanism a cut is produced from one side of the web to the other side. Although the cutting speed is very high as compared with the speed at which the flat material web travels, the cutting action performed normal to the feeding direction interferes with or blocks the web feeding action. Experience has shown that this cutting action causes shock waves to propagate in opposition to the feeding direction in the flat material web. In addition, distortion occurs in the plane of the flat material web about the instantaneous position of the cutting location extending transversely to the web. This distortion results from the fact that when looking at a cutting operation--the subsequently advanced web encounters no resistance in the area following the cutting location of the blade member, that is, the area where the severing cut has already taken place, while the subsequently advanced web encounters a maximum resistance at the instantaneous position of the cutting location. At the section not yet severed in the cutting direction ahead of the instantaneous position of the cutting location, the subsequently advanced web meets a resistance which is of an order of magnitude lying between the resistance values of the two previously described sections.
The disturbances generally referred to as shock waves propagate in opposition to the feeding direction of the flat material web and may cause unseating of the print head of a printer unit arranged in advance thereof, resulting in poor printing quality. Where bar code printers are used, the bar code pattern may cease to be readable.
The brake roll disclosed in U.S. Pat. No. 3,856,196 is relatively complex and has only its surface line in contact with the flat material web so there is no areal carries contact with the web and there is insufficient damping of the shock waves.
Cutting mechanisms of the prior art are detachably connected with a printer unit by a fastening means. In these arrangements, it is not possible to accurately define the position of the cutter section relative to the print head of the printer unit, nor the variation of the relative distance of the cutter section to the print head of the printer unit.